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Saturday, June 12, 2010

Book review: From Eternity to Here by Sean Carroll

From Eternity to Here: The Quest for the Ultimate Theory of TimeBy Sean CarrollDutton Adult (January 7, 2010)

Most of you will know Sean Carroll, who blogs at Cosmic Variance. Sean is a Senior Research Associate at CalTech and his research focuses on cosmology, general relativity and the standard model, as well as extensions thereof. He has written a textbook on General Relativity, and the lecture notes that gave rise to the book are available online. I've met Sean a few times, he's an interesting person and gives great talks. Sean has a special interest in the arrow of time, and that is also the topic of book “From Eternity to Here.” The arrow of time is, in a nutshell, the question why the past is different from the present.

I bought the book for three reasons. One is that for many years I've been using the PDF version of his lecture notes as a handy quick reference when on travel and had a bad consciousness for never buying the book. The second one is that from reading Sean's blog I know he writes well. The third reason is that adding a second book to the order rendered delivery free.

“From Eternity to Here” is a very well written book that communicates a lot of science, both textbook science and contemporary science, while at the same time being amazingly accurate. The biggest part of the book - all but the last chapter - is dedicated to accurately framing the question. Why is it interesting to ask why the past was what it was? What exactly is it that we don't understand? How do we get a grip on the problem? For this, Sean covers first of all the second law of thermodynamics, then special relativity, general relativity, cosmology, quantum mechanics, black hole physics, and finally inflation and the multiverse. In the last chapter, he then discusses possible solutions to the question he has posed and puts forward his own solution as the most plausible one. Along the way he scratches on topics like the vacuum energy, structure formation, the AdS/CFT duality and magnetic monopoles.

Sean is very careful with distinguishing between established science and unconfirmed speculations. The only glitch is the section on the holographic principle where he fails to point out that there is no experimental evidence for such a feature of Nature to be true in all generality. I am somewhat sick of being misinterpreted on this point so let me be very clear here. All I am saying is that, absent experimental evidence, scientists should be very careful with what they put forward as a true description of Nature. Theoretical evidence can very easily be biased simply because a topic that attracts attention may mount one-sided “evidence.” This can never replace actual tests of a hypothesis. The holographic principle certainly does not rest on the same basis as ΛCDM or the Schrödinger equation and I wish its status had been framed more clearly. Anyway, Sean needs the holographic counting of degrees of freedom for the rest of his argument.

I was very pleased that Sean's explanations of physical concepts are not as superficial and vague as one frequently finds in popular science books. He does not shy away from the phase space, using logarithms, and discusses the amplitude of the wave function. The chapter on quantum mechanics however somewhat suffers from the overuse of cats and dogs. The book has plenty of footnotes with additional explanations, and offers many references so that the interested reader will easily be able to find the relevant keywords and dig deeper, should they wish so. On several occasions I took a note that Sean had forgotten to point out a specific assumption that entered his argument or left out some exceptions. In every single case, these points were later addressed, so I am left with nothing to complain about.

I personally don't have a large interest in the topic and don't care very much about the whole discussion. I think the question is ill-posed and when we have a better understanding of quantum gravity we'll see why. Sean's book didn't succeed in increasing my interest. Nevertheless, it was a pleasure to read. Sean has a good sense of humor, but doesn't overdo it. The story he tells is also well embedded into its scientific history and I learned a thing or two here that I hadn't known before. Both the historical and the philosophical aspects however play a secondary role and don't take over the scientific discussion. All together, the book is very well balanced and a recommendable read. It has something to offer for anybody who has an interest in modern cosmology and/or the arrow of time. I'd give this book 5 out of 5 stars.

24 comments:

Thanks for your assessment of Sean’s book which has it framed so well I’ll have to go out and get a copy. As it happens other than your blog Sean’s is the one I look at the most frequently and have to agree his writing style and clarity being first rate. I liked what you said about his carefulness and it is this part of your evaluation I value and am intrigued by the most.

Feynman's sprinkler does not work if a video is run backwards and angular momentum is conserved. The Second Law and the Law of Large Numbers are unneeded. A strong arrow of time arises from quantum mechanics's origin.

A vacuum massed sector chiral background affects only resolved chiral bodies as an emergent phenomenon. Conservation of angular momentum would have a testable exception not contradicting prior observations.

Three small chemically and dimensionally identical balls are plated with superconductor and Meissner-effect levitated in hard vacuum. One ball is amorphous fused silica. The other two balls are quartz single crystals, one each in enantiomorphic space groups P3(1)21 and P3(2)21. Run the experiment for 24 hours as the Earth rotates on its axis and falls around the sun.

Despite having read Sean’s book you say you have no serious interest in the topic, so should we take that to mean you have no interest in time or no time for one? :-)

Oh by the way I’ve been amusing myself today with reading the recent paper you pointed to in your side bar by AMELINO-CAMELIA et Al, entitled “Taming nonlocality in theories with deformed Poincaré symmetry”. This paper of course is intended in large part as to be a shot across your bow in respect to challenging your own understanding of the nature of space and time, Not surprisingly I don’t understand their central criticism in such regard as calling your take on things as being “pre-Einsteinian”, while the formalism from which they move their own program forward from being that of Poincare’s, which in itself is pre-Einsteinian as being an attempt in maintaining a fixed reference frame..

To be honest most of their argument are totally lost on me, yet perhaps that’s more because I can’t imagine to begin with how a symmetry can be deformed and still be considered as one. Anyway it will be interesting what response you will eventually offer in respect to their criticism(s). It seems to me that with their key contention being the idealization of the coincidence of events needing to be abandoned that the very nature of time or more importantly causality itself can’t be avoided being addressed.

AC's newest paper is entirely off-topic here, so let me be brief. I'll write a reply to this which will probably be on the arxiv soon. I'll probably also have a blogpost summarizing the status since it's been getting somewhat confusing. AC's argument is so obviously wrong, it is almost sad. Quite ironically, the calculation in his paper is also in direct disagreement with one of his earlier papers (the calculation in the earlier paper was correct, just that he didn't come to the correct conclusion). You might have noticed that he cites Lee Smolin with a paper 'in preparation' (ref [16]) so there's more fun to come.

As to why I have no specific interest in the arrow of time, it's because I think there are more interesting questions to ask the answers to which we are more likely to find with our present knowledge, and these answers are necessary to address the puzzle of the arrow of time. That having been said, it's not that I don't think it's an interesting question, I just don't think it's a very promising topic to work on right now because too many pieces of the puzzle are still missing, so arguments are doomed to remain vague. Best,

My apologies for being off topic, yet it was meant more tongue in cheek as to indicate what you said in response, that it’s not so much you’re not having an interest in the nature of time, rather it stands as being one of the things you see as becoming better understood with the pursuit of more approachable concerns.

Anyway. despite everything else it appears my instincts were right in considering your paper holding more significance than perhaps even you thought/ it had. The beauty of it being of course it being inquiry founded in actual experiment, for which the precision and frequency of result will certainly increase over time. One of Einstein’s happy thought’s in such regard was to ask what the world would look like if he could catch up with a light beam and this I see as a continuance of that thought. I would guess you never imagined that a self professed phenomilogical theorist could end up being at the centre of such a fire storm; shades of John Bell I would say ;-)

So what are we saying here? That if, like Atlas Shrugged, you take out the last chapter it's a darned good book?

Jus' teasing. I bought it and enjoy it very much. The footnotes are important and combined with the prose make it a very rich book. I learned for example that on a micro-time scale that entropy can in fact decrease, but only temporarily and the net effect is either zero net entropy change or an increase in same, hence the 2nd "Law".

Wonderful review, Bee. I give your review 5 out of 5 stars and the book 4.6 out of 5 stars. Always round up.

I agree with the review: The book is worthwhile to read even if you are not interested in or disagree with the main thesis about the arrow of time. While reading I marked statements that seem to explain something exceptionally well that is usually confusing, like, for example, about a black hole: "you have absolutly no choice but to continue on to the grim destiny of the singularity, because it lies ahead of you in time, not in some direction of space". (That's a fact that is usullay completly lost in all these rubber-membrane pictures.)

As I looked to the bookshelf for reading material I never did ever see his, although, I did know of his gathering for chapter reviews and stopped in.

As I linked earlier to Reverse Chronology the time issue raised by varying links put up by Sean culminating in his book, was a nice way in which to stretch the mind in relation to how artistically in literature and in movie media style this can be approached with regard to the idea of how time can be manipulated.

In a QGP stance, as I see it, the drive toward some kind of singularity( not always in the future but happening in various locations to amount too)) is the idea in my mind to have the "crossover point" demonstrated in particularization, as we see the faster then light entities manifested in template measures for examination. SNO, ICECUBE, and Pierre Auger designs. Gran Sasso.

Now cosmologically given the state of the universe what drives it to be considered "one way or another" and we may say that such entities dominant in the state of the universe described would have been exemplifications of the idea of these crossover points and how they are in measure in relation to the idea of particularization in cosmological designs.

So we are given so many events "to manifest" the characterization of the state of that universe?

This is what I saw of Sean's work as to manifesting as toward "some characterization and seeding of the universe" as it is speeding up?

What is there to be misinterpreted about the statement that there is no experimental evidence for the holographic principle?

As Bee wrote in her review the problem is not that "there is no experimental evidence for the holographic principle?" could be misinterpreted, the problem is that statement is not there.

Since Sean Carrol explains both well established theories like GR and QFT which had tremendous success when confronted with experiments, he also explains some highly speculative concepts that did not have any connection to experiments (yet). He promises his readers to clearly point out which is which. In the chaper "the holographic principle" he does not point out that that is a speculative concept. He does not say that it is an established theory either, but a statement like "this insight has been dubbed the holographic principle and was introduced by Nobel laureate 't Hooft" may mislead some readers, a disclaimer would have been nice. On the other side all readers who do care about this will know that anyway.

Let me add that I was deliberately very careful with my statement. I said there is "no experimental evidence for such a feature of Nature to be true in all generality." One could probably argue that there is some experimental evidence for AdS/CFT (from heavy ion & condensed matter exp), but that's not the holography Sean is talking about and that he needs for the rest of his argument. And yes, what I meant is exactly what Tim said, it might mislead some readers. Best,

Yes, that's right, I'm being excessively careful. When in doubt, I'll rather err on the side of accuracy than readability. In any case, in the introduction Sean makes a point out of stating that he'll carefully disentangle the established from the speculative and he does indeed a great job, except for this section of the book. That's why I'm mentioning it. Best,

I\ve never actually considered myself as a philosopher past the point that I don’t believe one can discover much about things while totally ignoring such considerations, even if that only be in its attempted negation. I’m not certain what philosophers Plato considers that Dr. Carrol has been influenced by, yet perhaps I may discover that once I’ve read his book, which I did pick up on the weekend. One thing for certain his take promises to be strongly in contrast with the Smolin/Unger view, which I will admit holding more resonance for at present with finding time as fundamental rather than simply a emergent phenomilogical aspect of some other more foundational quality of nature. However most of all I’m intrigued by what Bee had to say about Sean’s assessment of things as being a careful one and I would like to see this for myself.

One of the things I’d like to find out is if Sean is able to lessen the reason to believe that time is a dimension on equal footing with the spatial degrees of freedom or able to lessen them also fundamentally to have them as emergent as well. That’s to say although for instance many including myself have trouble with string theory having all those extra dimensions, it does stand to demonstrate that with any concept of reality one is forced to recognize both the existence as well as the number of them before anything else can be considered. So I guess what I’m curious to find is if Sean considers the pre-existence of dimension being necessarily fundamental and if so which those might be or if not how so. The way I have always looked at things it’s not enough that all have a place to start, yet also someplace to go, as to have them able to become.